RF Energy Radiation Devices

Abstract

In this RF energy radiation device, a control unit controls an oscillator and an electric power amplifier in accordance with reflection wave electric power fed back from a radiation element and detected by a detector, and sets the operation mode to a first control mode or a second control mode. In the first control mode, the oscillator oscillates a pulsed RF signal having a first pulse width and a first pulse period. In the first control mode, a protection circuit does not block traveling wave electric power. In the second control mode, the oscillator oscillates a pulsed RF signal having a second pulse width different from the first pulse width and having a second pulse period different from the first pulse period. Alternatively, the oscillator continuously oscillates an RF signal. In the second control mode, the protection circuit blocks traveling wave electric power when the reflection wave electric power exceeds a specific threshold value.

Description

[Technical Field]

[0001] The present disclosure relates to improving the reliability of RF energy emitting devices. [Background technology]

[0002] Conventional RF (radio frequency) energy radiating devices detect reflected wave power and suppress output power according to the level of the reflected wave power. Conventional RF energy radiating devices supply output signals as burst waves so that the reflected wave power does not exceed an allowable value. Supplying output power as burst waves means radiating RF energy by alternating between on periods during which output power is continued and off periods during which output power is stopped (see, for example, Patent Document 1).

[0003] Patent Document 2 describes an RF energy radiating device that protects the device with high precision through hardware control and software control based on the detected value of reflected wave power and the detected value of the temperature of an RF power element.

[0004] The RF energy radiating device described in Patent Document 2 includes a cavity for accommodating an object to be heated, an RF signal generating unit, an RF amplifying unit, a radiating element, a temperature sensor, and a control unit. The RF power element is, for example, a transistor included in an RF power amplifier that amplifies the RF signal, or an RF power connector that constitutes a power supply unit. When the RF energy radiating device includes a circulator, the RF power element further includes a terminator for consuming reflected waves.

[0005] Conventional RF energy radiating devices continuously perform heating operations when the load impedance between the device and the object to be heated is matched to a certain degree. Therefore, to protect the RF power element from reflected waves, the output power is reduced or the heating operation is stopped when a certain condition is met. As a result, some objects may not be heated sufficiently. The above-mentioned certain condition may be when a certain amount of reflected wave power is detected or when the ambient temperature of the RF power element rises above a certain value.

[0006] When RF power is supplied as a burst wave, the on-time is set so that the reflected power level falls within the tolerance range of the RF power element. In operations such as plasma ignition, the load impedance may be in a state that causes total reflection of RF energy at the start of operation.

[0007] For this reason, it has been common to install an external matcher, or to lower the output level at the start of operation and then gradually increase it to the specified value.When installing a matcher, the space required for the matcher and its cost have been obstacles to development.

[0008] When the output level is gradually increased to the specified value, sufficient energy is not obtained to generate plasma by radiating RF energy onto the dielectric surface. If the RF output power level is increased to obtain sufficient RF energy to generate plasma, it becomes difficult to protect the device.

[0009] Heating can be achieved by supplying output power as a burst wave while changing the on-time without changing the peak power. When RF power is insufficient, output power is supplied continuously instead of as a burst wave. Even in this case, it is difficult to protect the device.

[0010] An RF power element is, for example, a transistor included in an RF power amplifier for amplifying an RF signal, an RF power connector that constitutes a power supply, etc. If the RF energy radiating device includes a circulator, a terminator for absorbing reflected waves is also an RF power element.

[0011] The matching device includes not only a device including distributed constants and lumped constants for adjusting the load impedance, but also means for changing the angle and rotation angle of the radiating part for radiating microwaves. [Prior art documents] [Patent documents]

[0012] [Patent Document 1] Japanese Patent Application Publication No. 2018-142452 [Patent Document 2] Japanese Patent Application Laid-Open No. 2018-167408 Summary of the Invention

[0013] An object of the present disclosure is to provide an RF energy radiating device that is highly reliable for a load, that is, an object to be heated.

[0014] An RF energy radiating device according to one aspect of the present disclosure includes an oscillator, a power amplifier, a radiating element, a detector, a controller, and a protection circuit.

[0015] The oscillator oscillates an RF signal having a variable pulse width and a variable pulse period. The power amplifier amplifies the RF signal and outputs forward power. The radiating element radiates the forward power. The detector detects reflected power returning from the radiating element. The control unit controls the oscillator and the power amplifier in accordance with the reflected power to set the operation mode to a first control mode or a second control mode.

[0016] In the first control mode, the control unit performs pulse width control by setting the pulse width and pulse period to a first pulse width and a first pulse period, respectively, to intermittently output traveling-wave power. The control unit causes the oscillator to oscillate a pulsed RF signal having the first pulse width and the first pulse period. In the first control mode, the protection circuit does not shut down the power amplifier.

[0017] In the second control mode, the control unit performs pulse width control by setting the pulse width and pulse period to a second pulse width and a second pulse period, respectively, to intermittently output forward-wave power. The second pulse width is different from the first pulse width, and the second pulse period is different from the first pulse period. The control unit causes the oscillator to oscillate a pulsed RF signal having the second pulse width and the second pulse period, or causes the oscillator to oscillate the RF signal continuously.

[0018] In the second control mode, the protection circuit shuts off the power amplifier when the reflected wave power exceeds a predetermined threshold.

[0019] In the present disclosure, pulse width control is performed in the first control mode at the start of operation to prevent the oscillator from being damaged. The RF energy radiating device continues its operation until the load impedance of the heated object stabilizes. In the pulse width control, the pulse time to prevent the oscillator from being damaged is varied according to the temperature of the oscillator. According to the present disclosure, the reliability of the RF energy radiating device can be improved. [Brief explanation of the drawings]

[0020] [Figure 1] FIG. 1 is a schematic diagram of an RF radiation energy device according to a first embodiment of the present disclosure. [Figure 2] FIG. 2 is a block diagram showing the protection circuit and its peripheral components in the RF radiant energy device according to the first embodiment. [Figure 3] FIG. 3 is a diagram showing an operation sequence in the RF radiant energy device according to the first embodiment. [Figure 4] FIG. 4 is a diagram showing an operation sequence in the RF radiant energy device according to the first embodiment. [Figure 5] FIG. 5 is a diagram showing an operation sequence in the RF radiant energy device according to the first embodiment. [Figure 6] FIG. 6 is a flowchart showing the operation of the RF radiant energy device according to the first embodiment. [Figure 7] FIG. 7 is a diagram illustrating an operation sequence of the RF radiant energy device according to the second embodiment of the present disclosure. [Figure 8] FIG. 8 is a flowchart showing the operation of the RF radiant energy device according to the second embodiment. [Figure 9] FIG. 9 is a diagram showing frequency characteristics of reflectance obtained by frequency sweeping in the RF radiant energy device according to the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0021] A RF energy radiating device according to a first aspect of the present disclosure includes an oscillator, a power amplifier, a radiating element, a detector, a controller, and a protection circuit.

[0022] The oscillator oscillates an RF signal having a variable pulse width and a variable pulse period. The power amplifier amplifies the RF signal and outputs forward power. The radiating element radiates the forward power. The detector detects reflected power returning from the radiating element. The control unit controls the oscillator and the power amplifier in accordance with the reflected power to set the operation mode to a first control mode or a second control mode.

[0023] In the first control mode, the control unit performs pulse width control by setting the pulse width and pulse period to a first pulse width and a first pulse period, respectively, to intermittently output traveling-wave power. The control unit causes the oscillator to oscillate a pulsed RF signal having the first pulse width and the first pulse period. In the first control mode, the protection circuit does not shut down the power amplifier.

[0024] In the second control mode, the control unit performs pulse width control by setting the pulse width and pulse period to a second pulse width and a second pulse period, respectively, to intermittently output forward-wave power. The second pulse width is different from the first pulse width, and the second pulse period is different from the first pulse period. The control unit causes the oscillator to oscillate a pulsed RF signal having the second pulse width and the second pulse period, or causes the oscillator to oscillate the RF signal continuously.

[0025] In the second control mode, the protection circuit shuts off the power amplifier when the reflected wave power exceeds a predetermined threshold.

[0026] The RF energy radiating device of this aspect can continue to operate even if the forward wave power is almost totally reflected at the start of operation, thereby improving the reliability of the RF energy radiating device.

[0027] In a second aspect of the present disclosure, in addition to the first aspect, in a first control mode, the control unit causes the oscillator to oscillate a pulsed RF signal having a first pulse rate, and the control unit causes the power amplifier to output pulsed traveling-wave power having the first pulse rate.

[0028] In the second control mode, the control unit causes the oscillator to oscillate a pulsed RF signal having a second pulse rate slower than the first pulse rate, or the control unit causes the oscillator to oscillate a continuous RF signal, and the control unit causes the power amplifier to output pulsed forward power having the second pulse rate or continuous forward power.

[0029] The protection circuit includes a converter and a gate controller. The converter blocks pulsed reflected power having a first pulse rate and does not block pulsed reflected power having a second pulse rate or continuous reflected power. The gate controller blocks forward-wave power in response to an output signal from the converter.

[0030] According to this aspect, in the first control mode, the forward power is not cut off even if the reflected power exceeds a predetermined threshold. That is, in the first control mode, the protection circuit does not function regardless of the reflected power. In the second control mode, the protection circuit functions depending on the reflected power.

[0031] In an RF energy radiating device according to a third aspect of the present disclosure, in addition to the first aspect, the control unit transitions the operation mode from the first control mode to the second control mode after a predetermined period has elapsed since the load state stabilized in the first control mode, and after transitioning the operation mode from the first control mode to the second control mode, the control unit transitions the operation mode from the second control mode to the first control mode in accordance with the load state.

[0032] According to this aspect, when the load state becomes unstable after it has stabilized, the operation mode can be set to the first control mode again.

[0033] In an RF energy radiating device according to a fourth aspect of the present disclosure, in addition to the first aspect, the control unit determines the stability of the load state based on the reflected wave power, and causes the oscillator to vary the pulse width and pulse period of the RF signal. The control unit changes the threshold voltage for determining the stability of the load state according to the pulse width and pulse period.

[0034] The converter determines the stability of the load state based on the reflected power. The tolerance range of the RF power element for the reflected power varies depending on the pulse width and pulse period of the pulse-width-controlled forward power and the ambient temperature of the RF power element. According to this aspect, the threshold voltage can be changed depending on these conditions.

[0035] If the pulse duration of the pulsed reflected power is shorter than the response time of the A / D converter of the processor, the conversion unit converts the pulsed reflected power into a voltage, thereby determining the stability of the load state.

[0036] According to a fifth aspect of the present disclosure, in addition to the first aspect, an RF energy radiating device further includes a memory for storing unstable times and stable times in a load state as a lookup table, and a control unit for varying a pulse width or a pulse period of a pulsed RF signal oscillated by the oscillator based on the lookup table and the elapsed operating time.

[0037] Specifically, the memory stores a lookup table of processing for stable and unstable load conditions in the first and second control modes, with various data previously obtained through experiments as setting conditions, thereby enabling the termination of RF energy emission without determining the stability of the load condition.

[0038] If the pulse time of the reflected wave power is shorter than the response time of the A / D converter of the processor, it is difficult to determine the stability of the load state, so this embodiment is effective as a control method in such cases. Below are examples of various data to be stored in memory as a lookup table.

[0039] For the first control mode, the following setting conditions are stored in a look-up table depending on the ambient temperature of the RF power element: 1. output power, 2. frequency, 3. frequency sweep interval, 4. operating time, 5. pulse time, 6. pulse period, and 7. pulse duty ratio.

[0040] For the second control mode, the following setting conditions are stored in a lookup table according to the ambient temperature of the RF power element: 1. output power, 2. frequency, 3. operating time, 4. pulse time, 5. pulse period, 6. pulse duty ratio, and 7. threshold for determining load stability. Note that the pulse time in the second control mode is longer than that in the first control mode. Furthermore, the second control mode includes supplying continuous wave forward wave power in addition to pulse width control for supplying pulsed forward wave power.

[0041] In addition to the first aspect, the RF energy radiating device according to a sixth aspect of the present disclosure further includes a memory that stores in advance, as a lookup table, the frequencies of the RF signal that can stabilize the load state in association with the elapse of operating time.

[0042] The oscillator is capable of varying the frequency of the oscillating RF signal. The control unit causes the oscillator to vary the frequency based on the lookup table and the elapsed operating time. This aspect can promote stabilization of the load state.

[0043] In an RF energy radiating device according to a seventh aspect of the present disclosure, in addition to the features of the first aspect, the oscillator is capable of varying the frequency of the oscillating RF signal. The control unit determines the stability of the load state based on an output signal from the detector. The control unit causes the oscillator to vary the frequency of the RF signal over time. According to this aspect, frequency sweeping can promote stabilization of the load state.

[0044] According to an eighth aspect of the present disclosure, in addition to the first aspect, an RF energy radiating device further includes a terminator for terminating reflected wave power, and a temperature sensor for detecting temperatures of the power amplifier and the terminator. The oscillator is capable of varying the frequency of the oscillating RF signal.

[0045] In the first control mode, the control unit controls the oscillator to vary the pulse width or pulse period based on the temperatures of the power amplifier and the terminator. This provides a safe zone in which the power amplifier and the terminator are not destroyed by reflected power. This aspect improves the reliability of the RF energy radiating device.

[0046] In a ninth aspect of the present disclosure, in addition to the first aspect, the control unit controls the power amplifier to set the forward power during the on-time to a first power level and the forward power during the off-time to a second power level in pulse width control, the second power level being a non-zero power level lower than the first power level.

[0047] According to this aspect, during the OFF time of pulse width control, a certain amount of idling current can be continuously flowed to the output circuit of the power supply to the power amplifier 2a, thereby stabilizing the output voltage of the power supply to the power amplifier.

[0048] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings.

[0049] (Embodiment 1) FIG. 1 is a schematic diagram of an RF energy radiating device 100 according to a first embodiment of the present disclosure.

[0050] As shown in FIG. 1, the RF energy radiating device 100 includes an oscillator 1, a power amplifier 2, a detector 3, a circulator 4, a terminator 5, a temperature sensor 6, a radiating element 7, a processor 9, a protection circuit 20, and a memory 30.

[0051] The oscillator 1 includes two oscillators (1a, 1b). The power amplifier 2 includes two power amplifiers (2a, 2b). The detector 3 includes two detectors (3a, 3b). The circulator 4 includes two circulators (4a, 4b).

[0052] The terminator 5 includes two terminators (5a, 5b). The temperature sensor 6 includes four temperature sensors (6a, 6b, 6c, 6d). The radiating element 7 includes two radiating elements (7a, 7b).

[0053] Each of the oscillators 1a and 1b oscillates and outputs an RF signal. The power amplifiers 2a and 2b are respectively oscillation The received RF signal is amplified and output as forward wave power. Both detector 3a and detector 3b detect forward wave power and reflected wave power.

[0054] The forward power refers to RF energy traveling from power amplifiers 2a and 2b to radiating elements 7a and 7b via circulators 4a and 4b, respectively. The reflected power refers to RF energy traveling from radiating elements 7a and 7b back to circulators 4a and 4b, respectively.

[0055] Circulators 4a and 4b are arranged on the forward power path and the reflected power path. Circulators 4a and 4b protect power amplifiers 2a and 2b, respectively, from reflected power that fluctuates in response to load fluctuations on the heated object. Terminators 5a and 5b each have a specific impedance that acts as a load for the reflected power from circulators 4a and 4b.

[0056] The radiating element 7a radiates RF energy transmitted from the power amplifier 2a via the circulator 4a into the cavity 8. The radiating element 7b radiates RF energy transmitted from the power amplifier 2b via the circulator 4b into the cavity 8. An object to be heated placed in the cavity 8 is heated by the RF energy.

[0057] Temperature sensors 6a and 6b are arranged near power amplifiers 2a and 2b, respectively, to detect the temperatures of power amplifiers 2a and 2b. Temperature sensors 6c and 6d are arranged near terminators 5a and 5b, respectively, to detect the temperatures of terminators 5a and 5b.

[0058] The memory 30 is, for example, a semiconductor memory that stores software and data used by the processor 9. The data stored in the memory 30 includes a lookup table prepared in advance for setting RF energy appropriate for the temperatures detected by the temperature sensors 6a to 6d.

[0059] The processor 9 is a general-purpose microprocessor that functions as a control unit for controlling the RF energy radiating device 100. The processor 9 controls the oscillators 1a and 1b and the power amplifiers 2a and 2b in accordance with the temperatures detected by the temperature sensors 6a to 6d.

[0060] Specifically, the processor 9 controls the oscillators 1a and 1b to generate RF signals having any frequency within a predetermined frequency band. The processor 9 also controls the oscillators 1a and 1b to generate RF signals having variable pulse widths and variable pulse periods, thereby performing pulse width control. The pulse width control, pulse width, and pulse period will be described later.

[0061] In this embodiment, processor 9 can refer to the temperatures detected by each of temperature sensors 6a-6d, for example, 50 times per second. Processor 9 can output instructions to oscillators 1a, 1b and power amplifiers 2a, 2b in accordance with those temperatures, for example, 50 times per second. That is, the software control period (hereinafter referred to as the control period) in processor 9 is 20 ms.

[0062] The protection circuit 20 functions to protect the circuits within the device based on the forward and reflected powers detected by the detectors 3a and 3b and the temperatures of the temperature sensors 6a to 6d.

[0063] As described above, the reflected power that fluctuates due to load fluctuations reaches the terminator 5 via the circulator 4 and is consumed by the terminator 5. This reduces the impact of the reflected power on the power amplifier 2 and reduces changes in the characteristics of the power amplifier 2 due to load fluctuations. In this way, the circulator 4 protects the power amplifier 2.

[0064] However, the consumption of reflected power generates heat in the terminator 5, which limits the operation of the RF energy radiating device 100. Considering the lifespan of the terminator 5, the terminator 5 is used so that the temperature rise due to heat generation is within a safe range in the operating environment. Therefore, continuous use of the RF energy radiating device 100 is always limited when the level of reflected power is high.

[0065] 1, the RF energy radiating device 100 includes two systems of RF energy radiating devices having the same configuration. One of the two systems is provided on the side of the radiating element 7a, and the other is provided on the side of the radiating element 7b. The processor 9, the protection circuit 20, and the memory 30 are common to the two systems of RF energy radiating devices.

[0066] Hereinafter, only the RF energy radiating device 100a of the system on the radiating element 7a side will be described, and a description of the RF energy radiating device 100b of the system on the radiating element 7b side will be omitted.

[0067] FIG. 2 is a block diagram showing details of the protection circuit 20 of the RF energy radiating device 100a of this embodiment and components around the protection circuit 20.

[0068] 2, RF energy radiating device 100a includes oscillator 1a, power amplifier 2a, detector 3a, circulator 4a, terminator 5a, radiating element 7a, reflected wave power feedback 24, forward wave power feedback 25, second F-V conversion unit 26, first directional coupler 27, and second directional coupler 28. Detector 3a includes first detector 3a1 and second detector 3a2.

[0069] First directional coupler 27 is disposed between power amplifier 2a and circulator 4a. First directional coupler 27 transmits a portion of the forward power from power amplifier 2a to circulator 4a to first detector 3a1. First detector 3a1 detects the portion of the forward power and transmits the detected signal to forward power feedback 25. Forward power feedback 25 receives the signal from first detector 3a1 and detects the level of the forward power based on the signal.

[0070] The second directional coupler 28 is disposed between the circulator 4a and the terminator 5a. The second directional coupler 28 is configured to couple the reflected wave from the circulator 4a to the terminator 5a. electric power The second detector 3a2 detects a portion of the reflected wave power and transmits the detected signal to the second F-V converter .

[0071] Second F-V converter 26 is a low-pass filter that receives the signal from second detector 3a2 and outputs a smoothed signal. That is, second F-V converter 26 converts a portion of the reflected power detected by second detector 3a2 into a voltage level corresponding to the level of the reflected power. Reflected power feedback 24 detects the level of the reflected power based on the voltage level from second F-V converter 26.

[0072] The RF energy radiating device 100a further includes common components with the RF energy radiating device 100b, namely, a processor 9, a protection circuit 20, and a memory 30. The protection circuit 20 includes a first F-V conversion unit 21, a reflected wave power cutoff feedback circuit 22, and a gate control unit 23.

[0073] Like second F-V converter 26, first F-V converter 21 is a low-pass filter that receives a signal from second detector 3a2 and outputs a smoothed signal. That is, first F-V converter 21 converts a portion of the reflected wave power detected by second detector 3a2 into a voltage level that corresponds to the level of the reflected wave power.

[0074] The circuit constants of the first F-V converter 21 are set so that pulsed reflected power having a first pulse rate (described later) in the first control mode does not pass through. The circuit constants of the first F-V converter 21 are set so that pulsed reflected power having a second pulse rate (described later) in the second control mode and continuous reflected power pass through. Therefore, in the first control mode, the output power level from the first F-V converter 21 is always zero. On the other hand, in the second control mode, the first F-V converter 21 outputs a voltage level corresponding to the reflected power (see waveform (c) in FIG. 3).

[0075] That is, in the first control mode, the reflected wave power cutoff feedback 22 does not cut off the power amplifier 2a and the forward wave power is not cut off. In the second control mode, the reflected wave power cutoff feedback 22 cuts off the power amplifier 2a in accordance with the voltage level from the first F-V conversion unit 21 and cuts off the forward wave power.

[0076] The operation and function of the RF energy radiating device 100 configured as above will be described with reference to FIGS.

[0077] 3 shows an example of an operation sequence when the operation mode transitions from the first control mode to the second control mode. As shown in FIG. 3, at time T31, the processor 9 sets the operation mode to the first control mode and starts the operation of the RF energy radiating device 100a.

[0078] The processor 9 causes the oscillator 1a to oscillate an RF signal of a desired frequency and alternately turns on and off the power supply to the oscillator 1a. As a result, the oscillator 1a oscillates an RF signal by alternating between an on period during which the RF signal is continuously oscillated and an off period during which the RF signal oscillation is stopped. The processor 9 causes the power amplifier 2a to amplify the RF signal so that the RF energy reaches a desired output value.

[0079] As a result, in the first control mode, pulsed microwaves are supplied to the cavity 8 as traveling wave power.

[0080] Supplying pulsed microwaves (traveling wave power) means that the power amplifier 2a outputs microwaves (traveling wave power) while alternating between on-time and off-time. An on-time is a time during which the power amplifier 2a continuously outputs traveling wave power. An off-time is a time during which the power amplifier 2a stops outputting traveling wave power.

[0081] In this embodiment, supplying a pulsed microwave (traveling wave power) while adjusting the amplification degree of the RF signal and adjusting the on time and off time is called pulse width control. In pulse width control, the pulse width (pulse time) is the length of the on time, and the pulse period is the sum of the on time and the off time.

[0082] In other words, pulse width control means outputting a pulsed microwave (traveling wave power), that is, outputting a microwave (traveling wave power) intermittently.

[0083] On the other hand, supplying microwaves (traveling wave power) continuously without pulse width control is called supplying continuous wave microwaves (traveling wave power).

[0084] The processor 9 calculates the pulse width and pulse period based on the temperature of the terminator 5a measured by the temperature sensor 6c (see FIG. 1) and the safe temperature operating range of the terminator 5a, which is stored in advance in the memory 30.

[0085] If the RF energy radiating device 100a does not include the circulator 4a, the safe operating range of the power amplifier 2a is taken into consideration as a condition for setting the pulse width and pulse period. That is, in the first control mode, the pulse width and pulse period may be controlled based on the temperatures of the power amplifier 2a and the terminator 5a so as to provide a safe range in which the power amplifier 2a and the terminator 5a are not destroyed by the reflected wave power.

[0086] As shown by waveform (a) in FIG. 3, in the first control mode, RF energy is output as pulsed microwaves (traveling wave power) having a predetermined pulse width and / or a predetermined pulse period.

[0087] Waveform (b) in Fig. 3 is the output signal of second detector 3a2 and indicates a voltage corresponding to the reflected wave power detected by second detector 3a2. Waveform (c) in Fig. 3 is the output signal of first F-V conversion unit 21 and indicates a voltage corresponding to the reflected wave power that has passed through first F-V conversion unit 21. Waveform (d) in Fig. 3 is the output signal of reflected wave power feedback 24. This signal is a voltage indicating the level of reflected wave power detected by reflected wave power feedback 24 and is input to an A / D (analog / digital) converter of processor 9.

[0088] Typically, a second F-V converter 26 is placed before the reflected wave power feedback 24. The second F-V converter 26 functions as a low-pass filter (LPF) to remove noise such as power supply ripple. Waveform (d) in Figure 3 is the differentiated waveform after passing through the LPF.

[0089] The pulse width and pulse period in pulse width control are adjustable. For example, the pulse period can be set to any value within the range of 10 μs to 2 ms depending on the ambient temperature and load state of the terminator 5a. The threshold voltage for determining the stability of the load state can be changed by changing both the pulse width and / or the pulse period. The load response characteristics of the power supply to the oscillator 1a must also be taken into consideration, and the period optimal for the capacitance of the power supply conductor may be selected.

[0090] After starting in the first control mode, when the pulsed forward power is reflected almost completely, a pulsed reflected power is generated, as shown by the waveform (b) in FIG.

[0091] Due to its circuit constant, the first F-V converter 21 does not transmit pulsed reflected wave power in the first control mode. In the second control mode, the first F-V converter 21 transmits pulsed reflected wave power having a pulse speed slower than in the first control mode, and continuous reflected wave power.

[0092] In this embodiment, the pulse speed is the reciprocal of the pulse period in the pulse width control of the microwave. The pulse speed in the first control mode is called the first pulse speed, and the pulse speed in the second control mode is called the second pulse speed. The second pulse speed is slower than the first pulse speed.

[0093] In the second control mode, the processor 9 causes the oscillator 1a to oscillate a pulsed RF signal having a second pulse rate slower than the first pulse rate in the first control mode, or a continuous RF signal. As a result, in the second control mode, the radiating element 7a radiates pulsed forward power having a second pulse rate slower than the first pulse rate in the first control mode, or a continuous forward power.

[0094] The pulse width and pulse period in the first control mode are referred to as the first pulse width and first pulse period, respectively. The pulse width and pulse period in the second control mode are referred to as the second pulse width and second pulse period, respectively. The first pulse width and first pulse period are different from the second pulse width and second pulse period, respectively.

[0095] The first F-V conversion unit 21 is a filter circuit using passive elements (resistors, capacitors, and inductors), or may be an active filter that adaptively changes its time constant using passive elements, an operational amplifier, and a digital potentiometer.

[0096] In the first control mode, the first F-V converter 21 does not transmit a voltage equivalent to the protection threshold for reflected power to the reflected power cutoff feedback 22. As a result, even in a load state that causes total reflection, the processor 9 does not cut off the oscillator 1a. That is, in the first control mode, even if the level of reflected power detected by the second detector 3a2 exceeds a predetermined threshold, the oscillator 1a does not cut off the RF energy.

[0097] This allows the RF energy radiating device 100a to continue operating without stopping even when the load state is unstable.

[0098] In the first control mode, when the output signal of the reflected wave power feedback 24 shown in waveform (d) of Figure 3 becomes equal to or less than the first threshold, the processor 9 determines that the load condition is stable (time T32). The first threshold is a predetermined threshold for determining the load condition by software. Determining the load condition by software means that the processor 9 determines the stability of the load condition based on the output signal of the reflected wave power feedback 24 shown in waveform (d) of Figure 3.

[0099] When the load condition stabilizes, the processor 9 transitions the operating mode from the first control mode, in which pulsed microwaves are radiated, to the second control mode, in which continuous forward wave power is radiated. In the second control mode, pulsed forward wave power or continuous forward wave power is output. The pulsed microwaves in the second control mode have different pulse widths and pulse periods from those in the first control mode, and have a slower pulse speed than those in the first control mode.

[0100] In the case of continuous wave microwaves, the reflected wave power detected by the second detector 3a2 is transmitted to the reflected wave power cutoff feedback 22 via the first F-V conversion unit 21.

[0101] In the second control mode, the load condition may become unstable, causing the reflected power to increase. Therefore, the reflected power cutoff feedback 22 determines whether the level of the reflected power exceeds a predetermined threshold set in hardware. If the reflected power exceeds this threshold (see waveform (c) in FIG. 3), the gate control unit 23 cuts off the power amplifier 2a (see waveform (a) in FIG. 3).

[0102] In this way, the protection circuit 20 operates to protect the RF power element from the reflected power. After that, no further determination is made as to whether the protection circuit 20 should be activated.

[0103] In order to maintain the stability of the load state in the first control mode, the first control mode may be continued for a predetermined period after the load state has stabilized, and then the operation mode may be switched from the first control mode to the second control mode.

[0104] In the second control mode, the first F-V converter 21 outputs the input reflected power as is. When the reflected power cutoff feedback 22 detects that the level of the reflected power exceeds a predetermined threshold, the gate controller 23 cuts off the power amplifier 2a (time T33). This stops the emission of RF energy and protects the terminator 5a from excessive reflected power.

[0105] An example of the hardware configuration of the reflected wave power cutoff feedback 22 is a comparator. The safe operating range of the terminator 5a changes depending on the ambient temperature. For this reason, the processor 9 varies the threshold voltage of the comparator via a D / A (digital / analog) converter.

[0106] If the reflected wave power increases after the operation mode has transitioned to the second control mode, the processor 9 may switch the operation mode back to the first control mode from the second control mode. Figure 4 shows the operation sequence in this case. Waveforms (a) to (d) in Figure 4 are signals corresponding to waveforms (a) to (d) in Figure 3, respectively. The vertical and horizontal axes of waveforms (a) to (d) in Figure 4 are the same as those of waveforms (a) to (d) in Figure 3, respectively.

[0107] In Fig. 4, the signal states shown in waveforms (a) to (d) in Fig. 4 from time T41 to just before time T43 are the same as those in waveforms (a) to (d) in Fig. 3. Therefore, only the period from time T43 onwards will be described.

[0108] As shown in waveform (d) of Figure 4, at time T43, the reflected wave power feedback 24 determines that the output signal of the first F-V converter 21 has exceeded the second threshold. The second threshold is a predetermined threshold higher than the first threshold, which is used by software to determine the load state. In this case, the operating mode transitions from the second control mode to the first control mode.

[0109] The processor 9 continues operation in the first control mode until the load is stabilized by pulse width control that allows the terminator 5a to operate within its safe operating range. As described above, stabilizing the load state means that the output signal of the reflected power feedback 24, shown in waveform (d) of Figure 4, is below the first threshold.

[0110] At time T44, when the output signal of the reflected wave power feedback 24 shown in waveform (d) in Fig. 4 becomes equal to or less than the first threshold, the processor 9 determines that the load state has stabilized. Once the load state has stabilized, the processor 9 again transitions the operation mode from the first control mode to the second control mode.

[0111] In the first control mode, shortening the pulse period allows the RF power element to continue operating within its safe operating range against reflected power. Depending on the load response characteristics of the power supply, the current may increase suddenly at the rise of the forward power during pulse width control. This may transiently suppress the output voltage of the power supply to the power amplifier 2a. In this case, the forward power is turned off before it reaches the desired value.

[0112] Figure 5 shows the operation of pulse width control to solve this problem. Sequence5 shows an example. Waveforms (a) to (d) in FIG. 5 are signals corresponding to waveforms (a) to (d) in FIG. 3, respectively. The vertical and horizontal axes of waveforms (a) to (d) in FIG. 5 are the same as those of waveforms (a) to (d) in FIG. 3, respectively.

[0113] As shown in Fig. 5, from time T51 to time T52, the level of the forward power during the on time in pulse width control is set to the same first power level as in Fig. 3. On the other hand, the forward power during the off time is set to a second power level that is not zero and is lower than the first power level. The second power level is a power level that does not affect the object to be heated.

[0114] In this way, a certain amount of current can continue to flow through the output circuit of the power supply to the power amplifier 2a during the off time in pulse width control, thereby stabilizing the output voltage of the power supply to the power amplifier 2a.

[0115] In Fig. 5, after the operation mode has shifted to the second control mode, the process is the same as in Fig. 3. When reflected wave power cutoff feedback 22 detects that the level of reflected wave power has exceeded a predetermined threshold, gate control unit 23 cuts off power amplifier 2a (time T53).

[0116] In the example shown in Fig. 5, the on / off ratio, i.e., the ratio of the first power level to the second power level of the forward power, can be adjusted within a range of 20dB to 30dB. Therefore, in the case of a forward power of 250W, a forward power of 0.25W to 2.5W is output during the off time. This on / off ratio is set appropriately depending on the level of the forward power.

[0117] In the example shown in FIG. 5, the detector 3a includes a logarithmic amplifier with an input range of 20 dB, and the range that can be converted into a voltage relative to the input power is about 20 dB.

[0118] Even if forward wave power of 0.25 W to 2.5 W is totally reflected and input to the second detector 3a2 as reflected wave power, the output voltage of the second detector 3a2 does not affect the first control mode.

[0119] The temperature sensor 6c (see FIG. 1) monitors the temperature of the terminator 5a. If the load condition is unstable and the temperature of the terminator 5a is detected to be outside the safe operating range, the processor 9 stops operation of the RF energy emitting device 100a.

[0120] FIG. 6 is an example of a flowchart showing the operation of the RF energy radiating device 100a according to this embodiment.

[0121] When the RF energy radiating device 100a starts operating, the processor 9 sets the operation mode to the first control mode in step S61. The processor 9 causes the oscillator 1a to oscillate an RF signal having a desired frequency. At the same time, the processor 9 causes the power amplifier 2a to amplify the RF signal so that RF energy at a desired output level is output.

[0122] In the first control mode, the processor 9 outputs RF energy using pulse width control. The duty in pulse width control is set to 50%. The duty is the ratio of the on time to the total of the on time during which RF energy is continuously output and the off time during which the output of RF energy is stopped.

[0123] In the first control mode, when the processor 9 determines from the output signal of the reflected wave power feedback 24 that the load state is stable by software (determined as "stable" in step S62), it transitions the operation mode to the second control mode. In the second control mode, the processor 9 controls the oscillator 1a and the power amplifier 2a to emit continuous forward wave power. The processor 9 starts counting the operation time and performs operation in the second control mode (step S63).

[0124] In the first control mode, if the software determines that the load state is not stable (determined as "unstable" in step S62), the processor 9 takes into consideration the temperature of the terminator 5a (step S64). If the temperature of the terminator 5a is detected to be outside the safe operating range (determined as "above specified value" in step S64), the processor 9 stops the operation of the RF energy radiating device 100a (step S65).

[0125] As described above, when the second control mode is performed in step S63, the reflected wave power cutoff feedback circuit 22 monitors the output voltage of the first F-V conversion unit 21 (step S66). If the level of the output signal from the first F-V conversion unit 21 exceeds a predetermined threshold (determined as "unstable" in step S66), the processor 9 regards this state as a sudden load change and monitors the temperature of the terminator 5a (step S68). If the temperature of the terminator 5a is detected to be outside the safe operating range (determined as "above specified value" in step S68), the processor 9 stops operation of the RF energy radiating device 100a (step S69).

[0126] Furthermore, when the timer count for the operation time in the second control mode reaches zero (determined "count zero" in step S66), the processor 9 stops the operation of the RF energy radiating device 100a (step S67).

[0127] In step S64, the terminator 5a If the temperature is detected to be within the safe operating range (determined in step S64 as "below the specified value"), the processor 9 returns the process to step S61. 5a If the temperature is detected to be within the safe usage range (determined in step S68 as "below the specified value"), processor 9 returns the process to step S61.

[0128] The memory 30 may store in advance, as a look-up table, the unstable time and stable time in the load state associated with the elapsed operating time. The processor 9 may cause the oscillator 1a to vary the pulse width or pulse period of the pulsed RF signal based on the look-up table and the elapsed operating time.

[0129] The unstable load state time is the length of the period during which the load state is unstable, and is determined in advance by experiment. The stable load state time is the length of the period during which the load state is stable, and is determined in advance by experiment. In other words, the processor 9 can switch the operation mode by feedforward control based on a lookup table, rather than feedback control based on reflected wave power.

[0130] The RF energy radiating device 100a executes the first control mode and the second control mode by means of hardware and software.

[0131] In the first control mode, pulse width control is performed. In pulse width control, the pulse time is set so that when the forward power is totally reflected, the reflected power falls within the allowable range of the RF power element. In this embodiment, the RF power element includes an oscillator 1a, a power amplifier 2a, and a terminator 5a. The pulse time is set so that the temperature rise of the RF power element during operation of the RF energy radiating device 100a falls within the safe operating range of the RF power element.

[0132] The RF energy radiating device 100a includes components for stopping the protection circuit 20 for protecting the RF power element from reflected power in the first control mode. The components include a first F-V conversion unit 21 and a second F-V conversion unit 26.

[0133] In the second control mode, the RF energy radiating device 100a radiates pulsed forward power having a slower pulse rate than in the first control mode, or continuous forward power, thereby protecting the RF energy radiating device 100a from the level of reflected power and the temperature rise of the temperature sensor.

[0134] As a result, in the first control mode, operation can be continued until the load impedance becomes stable for an object to be heated that has load characteristics that cause total reflection.

[0135] After the load impedance is stabilized, the operation mode shifts to the second control mode. In the second control mode, RF energy can be continuously emitted for a required time. It is also possible to adaptively change the safe operating range of the RF power element according to the ambient temperature of the RF power element. Note that stabilizing the load impedance means that the load impedance is in a range close to the output impedance of the RF energy radiating device 100a.

[0136] (Embodiment 2) Hereinafter, an RF energy radiating device 100a according to a second embodiment of the present disclosure will be described. The RF energy radiating device 100a according to this embodiment has the same configuration as that of the first embodiment. This embodiment differs from the first embodiment in that when the RF energy radiating device 100a starts operating, the processor 9 first performs frequency sweep.

[0137] 7 shows an operation sequence of the RF energy radiating device 100a according to the second embodiment of the present disclosure. As shown in waveform (a) of FIG. 7, when the RF energy radiating device 100a starts operating, the processor 9 performs frequency sweep in the first control mode (time T71).

[0138] In frequency sweeping, the processor 9 causes the oscillator 1a to oscillate an RF signal while sequentially changing the frequency at predetermined frequency intervals across a predetermined frequency band (for example, 2.4 GHz to 2.5 GHz).

[0139] Specifically, as shown in waveform (a) of Figure 7, oscillator 1a first oscillates microwaves at frequency F1 for a predetermined on-time, and then stops operating after that time has elapsed. After a predetermined off-time, oscillator 1a oscillates microwaves at frequency F2 for a predetermined on-time, and then stops operating after that time has elapsed. In this way, oscillator 1a sequentially oscillates RF signals having frequencies F1 to F8 with predetermined pulse widths and pulse periods (time T71 to time T72).

[0140] When n is a natural number between 1 and 7, the frequency Fn+1 is greater than the frequency Fn, and the frequency interval between the frequency Fn+1 and the frequency Fn is constant.

[0141] The oscillator 1a may be configured with a voltage-controlled oscillator (VCO) and a phase-locked loop (PLL), or may be configured with a direct digital synthesizer (DDS) with a fast frequency shift time. The choice of which depends on the pulse period of the pulse width control used. Furthermore, the period of frequency change in frequency sweeping depends on the control period of the processor 9.

[0142] The second detector 3a2 detects the level of the reflected wave power for any one of the frequencies F1 to F8 within a control period. The information is input to the A / D (analog / digital) converter of the processor 9 via the reflected wave power feedback 24.

[0143] The processor 9 selects the frequency that produces the smallest reflected wave power among the reflected wave powers measured during the frequency sweep, or a frequency close to that frequency, as the frequency to be used (time T72). The processor 9 performs pulse width control in the first control mode using microwaves having the frequency selected as the frequency to be used. In the waveform (a) of Figure 7, frequency F5 is selected as the frequency to be used.

[0144] When the load condition stabilizes and the reflected power falls below a predetermined threshold for software determination, the processor 9 transitions the operating mode from the first control mode to the second control mode (time T73). As described above, the load condition stabilizing means that the output signal of the reflected power feedback 24, shown in waveform (d) of Figure 7, falls below the first threshold.

[0145] By promoting stabilization of the load state through variable frequency control, the operation mode can be shifted from the first control mode to the second control mode more quickly. This improves the reliability of stabilization of the load state. As a result, when emitting RF energy such as for plasma ignition, it is possible to search for a frequency that is more likely to ignite quickly from a state of total reflection, thereby improving the ignition probability.

[0146] In this embodiment, similarly to the first embodiment (see FIG. 4), if the load state becomes unstable after transition to the second control mode, the processor 9 transitions the operation mode to the first control mode and performs frequency sweep again, thereby making it possible to search again for a frequency that can stabilize the load state.

[0147] FIG. 8 is a flowchart showing the operation of the RF energy radiating device 100a of this embodiment.

[0148] At the start of operation of the RF energy radiating device 100a, in step S81, the processor 9 sets the operation mode to the first control mode and causes the oscillator 1a to oscillate an RF signal for frequency sweeping. At the same time, the processor 9 causes the power amplifier 2a to amplify the RF signal and output RF energy at a desired output level.

[0149] In the present embodiment, in the first control mode, the pulse width in pulse width control is set to half the pulse period, that is, the duty in pulse width control is set to 50%.

[0150] In step S82, the processor 9 selects a frequency to be used by frequency sweeping, and continues pulse width control using a microwave having the frequency selected as the frequency to be used.

[0151] In the first control mode, when the processor 9 determines from the output signal of the reflected wave power feedback 24 that the load state is stable by software (determined as "stable" in step S83), it transitions the operation mode to the second control mode. In the second control mode, the processor 9 controls the oscillator 1a and the power amplifier 2a to emit continuous forward wave power. The processor 9 starts counting the operation time and performs operation in the second control mode (step S84).

[0152] In the first control mode, if the software determines that the load state is not stable (determined as "unstable" in step S83), the processor 9 takes into consideration the temperature of the terminator 5a (step S85). If the temperature of the terminator 5a is detected to be outside the safe operating range (determined as "above specified value" in step S85), the processor 9 stops the operation of the RF energy radiating device 100a (step S86).

[0153] As described above, when the operation of the second control mode is performed in step S84, reflected wave power cutoff feedback circuit 22 monitors the output voltage of first F-V conversion unit 21 (step S87). If the level of the output signal of first F-V conversion unit 21 does not exceed the predetermined threshold (determined "stable" in step S87), processor 9 returns the process to step S84.

[0154] If the level of the output signal from the first F-V converter 21 exceeds a predetermined threshold (determined as "unstable" in step S87), the processor 9 regards this state as a sudden load change and monitors the temperature of the terminator 5a (step S89). If the temperature of the terminator 5a is detected to be outside the safe operating range (determined as "above specified value" in step S89), the processor 9 stops the operation of the RF energy radiating device 100a (step S90).

[0155] Furthermore, when the timer count for the operation time in the second control mode reaches zero (determined "count zero" in step S87), the processor 9 stops the operation of the RF energy radiating device 100a (step S88).

[0156] In step S85, if a temperature within the safe operating range of the terminator 5 is detected (determined "below the specified value" in step S85), the processor 9 returns the process to step S81. Similarly, in step S89, if a temperature within the safe operating range of the terminator 5 is detected (determined "below the specified value" in step S89), the processor 9 returns the process to step S81.

[0157] The processor 9 may perform frequency sweep again to select a frequency to be used, and perform the same operation again.

[0158] In this embodiment, as shown in Figure 7, the processor 9 performs a frequency sweep and selects frequency F5 as the frequency to be used. However, the present disclosure is not limited to this. The processor 9 may select the frequency to be used based on the reflectivity obtained during the frequency sweep.

[0159] FIG. 9 shows the frequency characteristics of the reflectance obtained by frequency sweeping. In FIG. 9, the horizontal axis represents the frequency of the forward power, and the vertical axis represents the reflectance. The reflectance is the ratio of the reflected power (Pr) to the forward power (Pf), and is an index of the load stability. As shown in FIG. 9, the processor 9 selects, for example, a frequency around 2.42 GHz, which provides the smallest reflectance, as the frequency to be used.

[0160] The memory 30 may store in advance the operating conditions (pulse width, frequency, operating time, etc.) of the pulse width control in the first control mode as a menu according to the type of object to be heated.

[0161] The memory 30 may store in advance, as a look-up table, the frequencies at which the load state can be stabilized, in association with the elapsed operating time. The processor 9 may cause the oscillator 1a to vary the frequency based on the elapsed operating time and the look-up table.

[0162] The processor 9 may receive a signal from the detector 3a, determine a frequency at which the load state can be stabilized, and cause the oscillator 1a to vary the frequency as the operating time elapses. [Industrial Applicability]

[0163] As described above, the RF energy radiating device according to the present disclosure can be applied to heating devices that require high accuracy in controlling the output of RF energy, such as commercial heating devices. [Explanation of symbols]

[0164] 1, 1a, 1b oscillators 2, 2a, 2b power amplifier 3, 3a, 3b detector 3a1 Detector 1 3a2 Second detector 4, 4a, 4b Circulator 5, 5a, 5b terminator 6, 6a, 6b, 6c, 6d Temperature Sensors 7, 7a, 7b Radiating elements 8 cavities 9 Processor (control unit) 20 Protection circuit 21 First F-V conversion section 22 Reflected wave power cutoff return 23 Gate control section 24 Reflected wave power feedback 25 Traveling wave power feedback 26 Second F-V conversion section 27 First directional coupler 28 Second directional coupler 30 memory 100, 100a, 100b RF energy radiating device

Claims

1. an oscillator configured to generate an RF signal having a variable pulse width and a variable pulse period; a power amplifier configured to amplify the RF signal to output forward power; a radiating element configured to radiate the traveling wave power; a detector configured to detect reflected power returning from the radiating element; a control unit configured to control the oscillator and the power amplifier in response to the reflected wave power, the control unit is configured to set the operation mode to a first control mode or a second control mode; the first control mode includes performing pulse width control to output the forward power by setting the pulse width to a predetermined pulse width and / or setting the pulse period to a predetermined pulse period, the second control mode includes performing the pulse width control to output the forward power by setting the pulse width to a pulse width different from that in the first control mode and setting the pulse period to a pulse period different from that in the first control mode, In the first control mode, the forward power is not cut off, and in the second control mode, the forward power is cut off when the reflected power exceeds a predetermined threshold. RF energy emitting devices.

2. Further comprising a protection circuit, In the first control mode, the control unit is configured to perform pulse width control in which the pulse width and the pulse period are set to a first pulse width and a first pulse period, respectively, and the forward power is output intermittently, and the control unit is configured to cause the oscillator to oscillate a pulsed RF signal having the first pulse width and the first pulse period, In the first control mode, the protection circuit is configured not to block the forward power; In the second control mode, the control unit is configured to perform the pulse width control to set the pulse width and the pulse period to a second pulse width and a second pulse period, respectively, and to output the forward power intermittently, the second pulse width being different from the first pulse width, the second pulse period being different from the first pulse period, the control unit is configured to cause the oscillator to oscillate a pulsed RF signal having the second pulse width and the second pulse period, or to cause the oscillator to continuously oscillate the RF signal; In the second control mode, the protection circuit is configured to cut off the forward wave power when the reflected wave power exceeds a predetermined threshold.

10. The RF energy emitting device of claim 1.

3. In the first control mode, the control unit is configured to cause the oscillator to oscillate the pulsed RF signal having a first pulse rate, and the control unit is configured to cause the power amplifier to output pulsed traveling-wave power having the first pulse rate; In the second control mode, the control unit is configured to cause the oscillator to oscillate the pulsed RF signal having a second pulse rate slower than the first pulse rate, or to cause the oscillator to continuously oscillate the RF signal, and the control unit is configured to cause the power amplifier to output pulsed forward power having the second pulse rate or continuous forward power; the protection circuit includes a conversion unit and a gate control unit; the converting unit is configured to block the pulsed reflected wave power having the first pulse speed, and not block the pulsed reflected wave power having the second pulse speed and the continuous wave reflected wave power; The gate control unit is configured to cut off the forward wave power in response to an output signal from the conversion unit.

3. An RF energy emitting device according to claim 2.

4. the control unit transitions the operation mode to the second control mode after a predetermined period has elapsed since the load state has stabilized in the first control mode, The control unit is configured to transition the operation mode from the first control mode to the second control mode, and then transition the operation mode from the second control mode to the first control mode in accordance with the load state.

10. The RF energy emitting device of claim 1.

5. The control unit is configured to determine the stability of a load state based on the reflected wave power and to cause the oscillator to vary the pulse width and the pulse period of the RF signal. The control unit is configured to change a threshold voltage for determining the stability of the load state in accordance with the pulse width and the pulse period.

10. The RF energy emitting device of claim 1.

6. a memory for storing, in advance, a look-up table of unstable and stable times in a load state in association with the elapse of an operating time; the control unit is configured to vary the pulse width or the pulse period of the pulsed RF signal oscillated by the oscillator based on the look-up table and the elapsed operation time.

3. An RF energy emitting device according to claim 2.

7. a memory for storing in advance, as a look-up table, the frequency of the RF signal that can stabilize the load state in association with the elapse of operation time; the oscillator is capable of varying the frequency of the oscillating RF signal; the control unit is configured to cause the oscillator to vary the frequency based on the look-up table and the elapsed operating time.

10. The RF energy emitting device of claim 1.

8. the oscillator is capable of varying the frequency of the RF signal to be oscillated, the control unit determines the stability of the load state based on the output signal from the detector, the control unit is configured to cause the oscillator to vary the frequency of the RF signal over an operating time.

10. The RF energy emitting device of claim 1.

9. a terminator configured to terminate the reflected wave power; a temperature sensor configured to detect a temperature of the power amplifier and the termination; the oscillator is capable of varying the frequency of the RF signal to be oscillated, the control unit is configured to, in the first control mode, cause the oscillator to vary the pulse width or the pulse period based on the temperatures of the power amplifier and the terminator so as to provide a safety area in which the power amplifier and the terminator are not destroyed by the reflected wave power.

10. The RF energy emitting device of claim 1.

10. the control unit is configured to cause the power amplifier to set the forward wave power during an on-time to a first power level and to set the forward wave power during an off-time to a second power level that is not zero and is lower than the first power level, in the pulse width control.

10. The RF energy emitting device of claim 1.

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